trivial: Fix warning in _json.c due to char being unsigned on some platforms

Author: segevfiner

Modules/_json.c

@@ -18,7 +18,7 @@ static PyTypeObject PyEncoderType;
 
 typedef struct _PyScannerObject {
     PyObject_HEAD
-    char strict;
+    int strict;
     PyObject *object_hook;
     PyObject *object_pairs_hook;
     PyObject *parse_float;